1. Field of the Invention
The present invention relates to a catalytic converter for cleaning exhaust gas and combustion gas generated from automobiles or the like and more particularly to a supporting structure for securing a long catalyst carrier to a casing.
2. Prior Art
In a conventional ceramic honeycomb catalytic converter, a vertical sectional view of a typical example of a supporting structure for supporting and securing a ceramic honeycomb catalyst carrier by using a casing is shown in FIG. 1. Numeral 1 designates a ceramic honeycomb catalyst carrier. The carrier 1 has an external shape of a cylinder, such as a circular cylinder and is provided with a plurality of minute holes passing through in the longitudinal direction thereof and arranged in a honeycomb shape so as to hold catalysts for cleaning exhaust gas and combustion gas on the wall surfaces of the minute holes. Numeral 2 designates a mesh washer formed from a knitted wire mesh. The mesh washers 2 are mounted as buffering members between a two-split metal casing 4 and the honeycomb catalyst carrier 1 so as to embrace the entire circumferences of shoulder portions disposed at both ends of the honeycomb catalyst carrier 1 in the longitudinal direction thereof. Numeral 3 designates a mesh supporter mounted as a buffering member between the outer peripheral surface of the honeycomb catalyst carrier 1 and the casing 4. The honeycomb catalyst carrier 1 is secured to the casing 4 via the mesh washers 2 at both ends thereof. The difference in thermal expansion and contraction between the ceramic honeycomb catalyst carrier 1 and the metal casing 4 is absorbed by the metal washers 2 used as buffering members.
These days, it is required that the length of the honeycomb catalyst carrier be extended to enhance the cleanliness of exhaust gas and combustion gas. In the conventional supporting structure described above, since the honeycomb catalyst carrier is secured to the casing at both ends thereof, the difference in thermal expansion and contraction between the honeycomb catalyst carrier and the casing over the entire length of the honeycomb catalyst carrier must be absorbed by the metal washers. Accordingly, as the length of the honeycomb catalytic carrier is extended, the mesh washers cannot absorb the difference in thermal expansion and contraction between the honeycomb catalyst carrier and the casing. Therefore, at high temperatures, the supporting structure loses force for carrying the ceramic honeycomb catalyst carrier having smaller thermal expansion, thereby allowing the honeycomb catalyst carrier to move in the casing and inducing the danger of cracking or chipping the catalyst carrier. If the supporting structure is designed to keep sufficient holding force during high-temperature expansion to prevent such a problem, the metal washers are compressed excessively at low temperatures, thereby inducing the danger of cracking and chipping the honeycomb catalyst carrier.
The present invention is intended to solve the above-mentioned problems. The object of the present invention is to provide a ceramic honeycomb catalytic converter having a catalyst carrier supporting structure which does not cause the problem of losing the supporting force for securing the catalyst carrier owing to the difference in thermal expansion and contraction between the ceramic honeycomb catalyst carrier and the metal casing embracing the carrier, thereby preventing the problem of cracking and chipping the honeycomb catalyst carrier even when the length of the honeycomb catalyst carrier is extended.